relay gets hot

Printed From: the12volt.com
Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=129278
Printed Date: May 17, 2025 at 1:40 PM

Topic: relay gets hot

Posted By: justfuz
Subject: relay gets hot
Date Posted: November 18, 2011 at 12:43 PM

I've installed a relay for my remote turn-on lead from the radio to power up the amplifers and cooling fans. I followed the diagram from this site and connected the remote turn-on from the radio to 86 and connected the ground to 85. I do not have the amplifiers installed yet so I have not connected the 12v to 87 or anything to 30. So when I power the radio on, I hear the relay click on. I've got about a 45 minute drive to work and once I get there, the relay is hot. I checked the ampeage of the remote turn-on from the radio and its at 215mA.

Is this normal for the relay to get hot?

Replies:

Posted By: i am an idiot
Date Posted: November 18, 2011 at 4:03 PM

They do get warm. Not sure if I would call it hot, but yes on getting warm.

Posted By: justfuz
Date Posted: November 18, 2011 at 4:06 PM

I can hold it in my hand so its not steaming hot but I don't know how hot it will get if I had the radio on for 1 hour +.

Posted By: oldspark
Date Posted: November 18, 2011 at 5:33 PM

Maybe it's been that hot for 40 minutes and will remain as hot.

It's dissipating up to 3W of heat due to its coil.
The final load will add little heat - that depends on the current and contact resistance (I think typically less them 5 milli-Ohms).